HR: 09:15h
AN: PP21D-06    [Abstracts]
TI: A High Resolution Absolute-dated Oxygen Isotope Record of the Past 7000 Years from Spring Valley Caverns, Southeastern MN, USA
AU: * Dasgupta, S
EM: rayx0082@umn.edu
AF: Department of Geology and Geophysics University of Minnesota, 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Edwards, R L
EM: edwar001@umn.edu
AF: Department of Geology and Geophysics University of Minnesota, 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Alexander, E C
EM: alexa001@umn.edu
AF: Department of Geology and Geophysics University of Minnesota, 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Cheng, H
EM: cheng021@umn.edu
AF: Department of Geology and Geophysics University of Minnesota, 310 Pillsbury Dr SE, Minneapolis, MN 55455 United States
AU: Dorale, J A
EM: jeffrey-dorale@uiowa.edu
AF: Department of Geoscience University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52245 United States
AB: Two stalagmites, SV982 (3 thousand years (kyr)-present) and SV983 (7.8 kyr­Vpresent), from Spring Valley Caverns, southeastern Minnesota, USA contain records of oxygen isotopic variation in that cave for the past 7 kyr, which have been measured with an average time resolution of 10 years. The two stalagmites show similar patterns of stable isotopic variations for the overlapping portions of the records. An absolute chronology was constructed for stalagmite SV983 using 36 ²³⁰Th dates (typical 2σ relative error of 2%) coupled with annual band counting. For SV982, only the past 270 years were studied and part of the record from 1998 to 1900 A.D. was compared with instrumental climate record from the nearby town of Spring Valley, Minnesota. The δ ¹⁸ values correlate positively with the local mean annual temperature but show no apparent correlation with mean annual precipitation. The δ ¹⁸ agree closely with other climate records from the region (Dorale J.A. et al. 1992 Science 258, 1626-1630; Laird K.R. et al. 1996 LO 41, 890-902) demonstrating their significance as regional palaeoclimatic indicators. Several abrupt decadal to centennial scale shifts in δ ¹⁸ values are found ranging in magnitude from 0.6‰ to 2.7‰. Preliminary dating shows that these abrupt shifts in δ ¹⁸ values are centered at 6.5 (2.7‰), 4.6 (1.9‰), 3.4 (1.8‰) and 0.5 kyr (1.3‰). The 3.4 kyr event shows heavier δ ¹⁸ values corresponding to increase in temperature while all the other events are associated with decrease in δ ¹⁸ values and hence, decrease in temperature. The 6.5 kyr event was a shift from a several-century long cooling trend to an equally long warming trend. Comparing our record with the GISP2 δ ¹⁸ record (Grootes, P.M. et al. 1997 JGR 102, 26455-26470) from Greenland we find notable similarities in the decadal and centennial scale events, while the long term trends are more pronounced in our record. The δ ¹⁸ record from Spring Valley Caverns appears to be the best available tool for studying the nature of long term as well as short term variability in mid- to late-Holocene climate in a mid-latitude continental setting.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1637 Regional climate change
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4914 Continental climate records
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005